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If you look at a piece of a leaf or a drop of saliva through a microscope, what do you see? Cells are the basic building blocks of life and they make up every living thing, from plants to animals, from humans to bacteria! In Cells: Experience the World at Its Tiniest, readers ages 12 to 15 investigate cells and learn how they affect our health, reproduction, criminal investigations, and agriculture. Through cell science, scientists have been able to create many things to help society, including seeds that grow better in certain locations, tools that can detect DNA at crime scenes, and immunizations to keep people healthy.To reinforce learning and encourage investigation, hands-on activities include finding and identifying bacteria from pond water and human mouths and building models of different types of cells. Links to online primary sources, videos, and other relevant websites provide a digital learning component that appeals to this age group and promotes further, independent learning while strengthening practical connections to the material. Additional materials include a glossary and a list of current reference works, websites, and Internet resources.

Informations

Publié par	Nomad Press
Date de parution	17 juillet 2017
Nombre de lectures	0
EAN13	9781619305236
Langue	English
Poids de l'ouvrage	6 Mo

Informations légales : prix de location à la page 0,0650€. Cette information est donnée uniquement à titre indicatif conformément à la législation en vigueur.

Extrait

Nomad Press
A division of Nomad Communications
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Copyright 2017 by Nomad Press. All rights reserved.
No part of this book may be reproduced in any form without permission in writing from the publisher, except by a reviewer who may quote brief passages in a review or for limited educational use .
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Educational Consultant, Marla Conn
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You can use a smartphone or tablet app to scan the QR codes and explore more! Cover up neighboring QR codes to make sure you re scanning the right one. You can find a list of URLs on the Resources page.
If the QR code doesn t work, try searching the Internet with the Keyword Prompts to find other helpful sources.
Cells
Contents
Timeline
Introduction
Cells Are Life
Chapter 1
How Do Cells Work?
Chapter 2
Discovering Single-Cell Life
Chapter 3
Growing Plants
Chapter 4
Explore Animal Cells
Chapter 5
The Human Side of Cell Science
Chapter 6
Cells Impact Medicine and Agriculture
Chapter 7
The Future of Cell Science
Glossary Metric Conversions Resources Index
TIMELINE
300s BCE
Aristotle supports the theory of spontaneous generation and writes widely of animals and nature.
1590s CE
Hans and Zacharias Janssen invent the first compound microscope.
1663
Robert Hooke describes cells when he discovers them in cork.
1665
Robert Hooke adds light to a compound microscope and publishes his book, Micrographie! .
1668
Antonie van Leeuwenhoek creates a simple microscope and discovers unicellular organisms.
1675-1679
Marcello Malpighi publishes several works on the early development of organisms. He is considered by many to be the father of embryology.
1802
Charles-Francois Brisseau de Mirbel proposes that plants are made up of cells.
1832
Barth lemy Dumortier observes plant cell division under a microscope. Robert Remak observes cell division in animal cells.
1833
Robert Brown discovers the cell nucleus.
1839
Matthias Jakob Schleiden and Theodor Schwann propose cell theory.
1842
Julius Robert von Mayer publishes the chemical formula for photosynthesis.
1858
Rudolf Virchow adds to cell theory by hypothesizing that all cells come from preexisting cells.
1859
Louis Pasteur disproves the theory of spontaneous generation.
1866
Gregor Mendel publishes his work on genetics and principles of inheritance.
1869
Friedrich Miescher discovers DNA.
1881
Theodor Engelmann discovers that photosynthesis occurs in the chloroplast.
1886
Ernst Abbe and Carl Zeiss invent the modern compound microscope.
1898
Camillo Golgi described the Golgi apparatus, an organelle in the cell.
1931
Ernst Ruska builds the first electron microscope.
1944
Scientists at the Rockefeller Institute for Medical Research show that all genes have DNA.
1952
Rosalind Franklin produces the first image of DNA.
1952
The first human cell line is created.
1955
The scanning electron microscope (SEM) is invented.
1962
James Watson, Francis Crick, and Maurice Wilkins receive the Nobel Prize for their discovery of DNA s structure.
1970s
Archaea are discovered to be a separate organism from bacteria and receive separate taxonomic classification.
1970s
Lynn Margulis publishes work on endosymbiotic theory.
1977
Frederick Sanger creates a DNA sequencing method.
1981
Transgenic mice and fruit flies are produced. A mouse embryonic stem cell line is established.
1983
Thomas Cech and Sidney Altman discover ribozymes.
1990
The Human Genome Project is started in an effort to map the entire human genome.
1996
A sheep named Dolly is the first animal to be cloned. Dolly survives for more than six years.
1998
Mice are cloned from adult stem cells.
1998
Researchers achieve the first animal genome sequence of the nematode worm.
1998
The National DNA Index System (NDIS) is created by the FBI.
2003
The human genome sequence is published.
2012
A new genetic tool called CRISPR-Cas9 allows for easy editing of sections of DNA.
2016
GMO labeling legislation is passed, requiring standard labels on genetically modified food.
Introduction
Cells Are Life

Why are cells important to the study of biology?

Cells are the building blocks of every form of life. Understanding cells is critical to understanding how living creatures function.
People believe what they can see. This has been true throughout human history. For example, thousands of years ago, people could see that the sun was in a different place in the sky depending on the time of day or time of year. They believed that the sun was moving across the sky.
For thousands of years, this was the accepted explanation, that the sun moved around the earth. Eventually scientists and thinkers proved that it was actually the earth in motion around the sun.
Hundreds of years ago, people noticed that mice appeared in the rags covering cheese and bread. It seemed that the combination of cheese and bread stored in a dark place created mice. This deduction might seem foolish to people today in the twenty-first century. But in the past, people made deductions on what they could see simply with their eyes.
Observations such as this led to a theory called spontaneous generation, which was first suggested by Aristotle (384-322 BCE). Aristotle was a Greek philosopher and scientist who made contributions to many areas, from physics and biology to mathematics and politics. His theory of spontaneous generation stated that some organisms develop from nonliving matter. For example, mice came from bread and cheese. Maggots came from rotting meat. Remember, people tend to believe what they can see!
Not everyone believed in spontaneous generation. Some people suspected that living things were made up of substances similar to what was found in a chemistry lab. However, there was no way to prove it. And from the time of Aristotle, it was understood that science must be observed and measurable to have meaning. It was this belief that led to the scientific method, the process scientists use to perform experiments and make discoveries.
Today, we know that maggots come from eggs that are laid by flies that are attracted to rotting meat. We also know that organisms, which are living things, do not come from nonliving matter. All living organisms, including bacteria, plants, and animals, come from other living things.

The questions remained: What is life? How do we prove something we can t see?

P RIMARY S OURCES

Primary sources come from people who were eyewitnesses to events. They might write about the event, take pictures, post short messages to social media or blogs, or record the event for radio or video. Why are primary sources important? Do you learn differently from primary sources than from secondary sources, which come from people who did not directly experience the event?

V OCAB L AB

There is a lot of new vocabulary in this book! Turn to the glossary in the back when you come to a word you don t understand. Practice your new vocabulary in the VOCAB LAB activities in each chapter.
Antonie van Leeuwenhoek s first microscope probably looked something like this.

THE INVENTION OF THE MICROSCOPE
Hans Janssen and his son, Zacharias, were eyeglass makers in the Netherlands in the 1590s. They discovered that if they placed two lenses at a distance from each other, the lenses magnified the object being studied. Using this discovery, they created the first compound microscope, a tube with lenses at both ends that could magnify objects up to nine times their size. During the next 50 years, other European scientists improved upon this design until objects could be magnified up to 30 times.
Another man from the Netherlands, Antonie van Leeuwenhoek, was a linen merchant in 1668. He wanted a way to examine super-fine linen fibers, so he began to work on a better lens.

The lens he developed showed cloth fibers in great detail.
Van Leeuwenhoek mounted a single lens in a brass holder about 3 to 4 inches long. Specimens mounted on a sharp point in front of the lens were magnified up to 200 times. This Dutch linen merchant had invented the world s first simple microscope. It s called a simple microscope because, unlike the compound microscope, only one lens is used.
It didn t take van Leeuwenhoek long to start looking at other things with his microscope. In a sample of saliva, he saw small organisms moving around. He called them animalcules. We know them as the one-celled organisms, bacteria. Van Leeuwenhoek might have been the first person to observe bacteria.
The enthusiastic amateur scientist shared his observations with the Royal Society of London. After his discovery of single-cell organisms was confirmed, he was appointed as a fellow of the Royal Society, the highest honor for scientists. He went on to create about 250 microscopes and he continued studying samples. Among his papers were descriptions of red blood cells, sperm cells, and protists.
While van Leeuwenhoek was creating the simple microscope, British scientist Robert Hooke (1635-1703) was doing his own inventing and observing. With the help of instrument maker Christopher Cook, Hooke created a microscope with a built-in light source. Why do you think Hooke wanted a light source built into the microscope?
Hooke s curiosity for examining items under the microscope was unstoppable. He viewed insects, hair, sand, snow, and plants. When he looked at a piece of cork from a tree, he saw dozens of empty spaces surrounded by walls. Hooke thought the spaces looked like small, plain rooms, like the cells in which monks lived in monasteries. Hooke called the walled spaces cells. Hooke reco